考虑致密储集层岩石及流体可压缩性和基质中流体的非线性渗流,建立了体积压裂致密储集层跨尺度渗流离散裂缝数值模拟模型,对模型进行了验证并进行了应用实例分析。模型采用两点流动近似方法计算传导率,并引入“星形-三角形”转换算法消除裂缝相交处的极细小网格,改善了计算稳定性。在时间域内采用全隐式离散,模型求解采用自动微分方法,提高了建模效率和计算精度。采用Eclipse软件模拟结果及新疆油田某致密储集层1口长体积压裂水平井的实际生产数据验证了模型的可靠性。实际应用结果表明,所建立模型能成功模拟大规模复杂缝网发育的储集层;缝网改造区越大,水平井产能越高;裂缝密度平面分布差异性及连通程度是影响致密油平面动用非均匀性的关键因素。图12参25
A discrete fracture model for multi-scale flow in large-scale fractured tight oil reservoirs is proposed considering the compressibility of reservoir rock and fluid, and the non-linear flow in the tight matrix. Validation of the model is performed, followed by the field application of the model. The two-point flux-approximation scheme is adopted in the model to calculate conductivity, and small grids at the fracture intersections are eliminated by the “star-delta” transformation method to improve the computational stability. The fully implicit discretization scheme is performed on the temporal domain. Automatic differentiation technique which can improve model establishment efficiency and computational accuracy is applied in the model to solve the numerical model. The model is validated with the simulation results of Eclipse and the historical production data of a long fractured horizontal well in a tight oil reservoir in Xinjiang oilfield. Simulation results of a field-scale reservoir show that the model proposed can simulate reservoirs with large-scale complex fracture systems; well productivity is positively correlated with the scale of the stimulated reservoir volume, and the difference in planar fracture density and fracture connectivity are proved to be the key factors that lead to the heterogeneous distribution of remaining oil in tight oil reservoirs.
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